Sintered porous plastic liquid barrier media and applications thereof

ABSTRACT

This application discloses porous self-sealing media comprising a sintered mixture of an absorbent material and a thermoplastic. The self-sealing media block passage of organic solvents or organic solvents in aqueous mixtures, wherein the organic solvents are at concentrations greater than about 40%. The self-sealing media also block acidic solutions. The self-sealing media are useful in a variety of applications such as a pipette tip filter, in line filter, vent, non-mechanical check valve, safety valve, and suction canister.

PRIOR RELATED APPLICATIONS

The present application claims the benefit of priority to U.S.Provisional Application No. 61/497,218 filed Jun. 15, 2011, which ishereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention provides sintered porous plastic media which areeffective in blocking passage of organic solvents, aqueous solutions ororganic solvents or acidic solutions.

BACKGROUND

Current commercially available self-sealing pipette tip filters canblock aqueous-based solutions containing up to about 40% by volumeorganic solvent, such as isopropanol (IPA) or dimethylsulfoxide (DMSO),from passing through the filter when the solution contacts the filterduring over pipetting. However, these self-sealing pipette tip filtersdo not block aqueous-based solutions containing organic solvents of morethan 40% from passing through the filter when the solution contacts thefilter during over pipetting. Accordingly, what is needed areself-sealing pipette tip filters that not only block pure water andwater based solutions containing less than 40% organic solvents, butalso block solutions that are organic solvents and aqueous mixtures,wherein the organic solvents are at concentrations greater than about40%. Also needed are self-sealing pipette tip filters that blocknon-aqueous based polar organic solutions. Also needed are self-sealingpipette tip filters that block pure polar organic solvents.

In addition to self-sealing pipette tip filters, self-sealing media arealso useful as non-mechanical check valves to prevent liquid frompassing through upon contact, such as in a suction canister. Currentnon-mechanical check valves have similar compositions as self-sealingpipette tip filters and do not block solutions that contain more than40% organic solvent and less than 60% of water. There is market need tohave non-mechanical valves that not only block pure water and waterbased solutions containing less than 40% organic solvents, but alsoblock solutions that are organic solvents and aqueous mixtures, whereinthe organic solvents are at concentrations greater than about 40%.Commercially available self-sealing media also do not block acidicaqueous solutions or organic acid solutions at low concentrations.Non-mechanical valves are needed that block non-aqueous based polarorganic solutions. Also needed are non-mechanical valves that block purepolar organic solvents. What is also needed are self-sealing media thatblock aqueous solutions of inorganic acids or organic acids atconcentrations of at least about 5%.

SUMMARY

The present invention solves these problems by providing sintered porousplastic self-sealing media that block various solvents and solutionsthereof. In one embodiment, these sintered porous plastic self-sealingmedia block organic solvents in aqueous mixtures, wherein the organicsolvents are at concentrations greater than about 40%, or between about40% to about 99%, or between about 40% to about 90%. The presentinvention also provides self-sealing media that block polar organicsolvent solutions that are not aqueous-based, including 100% pureorganic solvents. The present invention further provides self-sealingmedia that block aqueous solutions of inorganic acids or organic acidsat concentrations of from about 0% to about 100%. The present inventionalso provides self-sealing media that block aqueous solutions ofsurfactants at concentrations ranging from about 0% to about 100%. Thepresent invention also provides self-sealing media that block organicsolvents in aqueous mixtures with acids and/or surfactants.

In some embodiments, the porous plastic self-sealing media comprise anabsorbent material and a thermoplastic. In a specific embodiment, theabsorbent materials are polymeric materials that form high a viscositysolution quickly when contacted by water and polar organic solutions.This definition is different from traditional super-absorbent materialswhich are generally used for absorbing water. In one embodiment, theabsorbent material is polyacrylic acid (PAA). In one embodiment, the PAAis linear PAA with a molecular weight greater than 100 KDa orcross-linked PAA with a linear backbone molecular weight betweenadjacent crosslinks (Mc) greater than 10 KDa.

The porous self-sealing media may optionally include elastomericmaterials and/or color change indicators. The porous self-sealing mediamay further comprise another absorbent material, CMC or a superabsorbentmaterial.

The porous self-sealing media in embodiments of the present inventionare useful in a variety of applications and devices including but notlimited to the following: pipette tip filter, in line filter, vent,non-mechanical check valve, safety valve, and suction canister.

These porous self-sealing media that block organic solvents, acids,bases and surfactants help prevent unwanted spills and alsocontamination and corrosion of devices due to contact with organicsolutions, acids and bases.

Self-sealing media in this invention are defined as porous media thatallow air and gas to pass through when the media are dry and do notallow air, gas or solutions to pass through when the media contactsaqueous based or organic solvent-based liquid solutions, for exampleunder suction forces or pressure. The suction forces are vacuum ornegative pressures. The new organic solvent self-sealing media of thepresent invention can block inorganic and organic solutions containingorganic solvent concentrations of about 40% or greater. The presentinvention also provides self-sealing media that block aqueous solutionsof inorganic acids or organic acids at concentrations of from about 0%to about 100%. These self-sealing media also block passage of solutionscontaining bases or surfactants. Use of these self-sealing mediaprovides a safer environment for transfer of highly corrosive inorganicacids and organic acids.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic representation of a non-mechanical filter valve 10comprising a porous self-sealing media that blocks organic solventswhich could be used in a suction canister. The filter 10 comprises afirst portion 11 having an open end 12 and a second portion 13 having aclosed end 14

FIG. 2 is an exploded view of a suction canister lid containing thefilter 10 comprising a porous self-sealing media that blocks organicsolvents and a filter shield in accordance with one embodiment of theinvention. The filter 10 of the invention is adapted to be positionedwithin the conduit or passageway of a suction canister lid 20,particularly the underside of the lid, such that air flow (andeventually fluid) contacts the filter 10 at the flow path into thevacuum port 21 such that the filter 10 precedes the vacuum source andits associated tubing (not shown). The filter 10 in its “dry” statepermits the passage of air through the filter from the interior canisterenvironment and into the vacuum port 21 and environment beyond the lid20. The filter 10 of the invention can be coupled either directly orindirectly onto the underside of the lid 20. A filter shield 25,functions to both control the sequence of fluid contact to the filter 10and to secure the filter 10 to the underside of the lid 20. In oneembodiment the filter 10 and filter shield 25 of the invention areassembled by inserting the filter 10 in a longitudinal direction intothe filter shield 25 and attaching the filter shield 25 and filter 10(not shown) to the underside of the suction canister lid 20.Alternatively, the filter shield 25 can be attached to the canister lid20 first, and the filter 10 inserted therein after. The lid 20 can thenbe attached to the rim of a reservoir (not shown). In the case of thealternative embodiment wherein the filter shield is integrated as partof the lid, there is no filter shield attachment step. Associated tubingand attachments can be affixed onto various ports and openings of thelid, such as tubing for a tandem port, a cap for a pour spout, andvacuum tubing to the vacuum port.

FIG. 3 is a schematic representation of a filter 30 comprising a porousself-sealing media that blocks organic solvents for an in lineself-sealing gas or air filter 32. The arrow indicates the direction ofgas or airflow.

FIG. 4 is a schematic representation of a pipette tip containing afilter comprising a porous self-sealing media that blocks organicsolvents. FIG. 4 illustrates a modified pipette tip 40 which againcomprises a hollow, frustoconical or tapering tubular member 42 forsecuring to a suitable pipette or suction device 49 at one end 44 so asto draw a liquid sample into the pipette through the opposite end 46. Aplug member 48 is a porous self-sealing media that blocks organicsolvents and is positioned between a chamber above the media 47 and achamber below the media 45 which is continuous with end 46.

FIG. 5 is a schematic representation of two bilayered structures. In A(top panel) a porous media comprising a sintered porous thermoplasticlayer with absorbent is adjacent to a sintered porous thermo plasticlayer with no absorbent. In B (bottom panel) a porous media comprising asintered porous thermoplastic layer with absorbent and a color changeindicator is adjacent to a sintered porous thermoplastic layer with noabsorbent or color change indicator.

FIG. 6 is a schematic representation of two trilaminar structures. In A(top panel) a porous media comprising a sintered porous thermoplasticlayer with absorbent is adjacent on both sides to sintered porousthermoplastic layers with no absorbent. In B (bottom panel) a porousmedia comprising a sintered porous thermoplastic layer with absorbentand a color change indicator is adjacent on both sides to a sinteredporous thermoplastic layer with no absorbent or color change indicator.

FIG. 7 is a three-dimensional schematic representation of a self-sealingmedium in the form of a trilaminar disc. The individual layers couldcorrespond to the layers described in FIGS. 5 and 6.

DETAILED DESCRIPTION

The present invention solves these problems by providing sintered porousplastic self-sealing media that block various solvents and solutionsthereof. In one embodiment, these sintered porous plastic self-sealingmedia block organic solvents in aqueous mixtures, wherein the organicsolvents are at concentrations greater than about 40%, or between about40% to about 99%, or between about 40% to about 90%. The presentinvention also provides self-sealing media that block polar organicsolvent solutions that are not aqueous-based, including 100% pureorganic solvents. The present invention also provides self-sealing mediathat block aqueous solutions of inorganic acids or organic acids atconcentrations of from about 0% to about 100%. The present inventionalso provides self-sealing media that block aqueous solutions ofsurfactants at concentrations ranging from about 0% to about 100%. Thepresent invention also provides self-sealing media that block solutionsof bases at concentrations ranging from about 0% to about 100%. Thepresent invention also provides self-sealing media that block organicsolvents in aqueous mixtures with acids and/or surfactants.

The present invention provides porous self-sealing media that blockorganic solvents in aqueous mixtures, wherein the organic solvents areat concentrations greater than about 40%, or between about 40% to about99%, or between about 40% to about 90%, or between about 40% to about80%, or between about 40% to about 70% (vol %). The present inventionalso provides porous self-sealing media that block aqueous based polarorganic solutions or pure polar organic solvents. The present inventionalso provides porous self-sealing media that block polar organic solventsolutions that are not aqueous-based, including 100% pure organicsolvents. The present invention also provides porous self-sealing mediathat block aqueous solutions of inorganic acids or organic acids atconcentrations of from about 0% to about 100%, 0% to about 90%, 0% toabout 80%, 0% to about 70%, 0% to 60%, 0% to 50%, or 0% to 40%, orgreater than 5%. The present invention also provides porous self-sealingmedia that block the passage of aqueous solutions of bases. The presentinvention also provides porous self-sealing media that block aqueoussolutions of surfactants at concentrations of at least about 0% to about100%.

The self-sealing media of the present invention comprise an absorbentmaterial and a thermoplastic. The term plastic in this application isused interchangeably with the term thermoplastic. In one embodiment, thethermoplastic particles are selected from the group consisting ofpolyethylene, polypropylene and polyvinylidene fluoride (PVDF). In oneembodiment, the polyethylene is high density polyethylene (HDPE), lowdensity polyethylene (LDPE), very high molecular weight polyethylene(VHMWPE), or ultrahigh molecular weight polyethylene (UHMWPE). In oneembodiment, the absorbent material is polyacrylic acid (PAA). In oneembodiment, the PAA is linear PAA with a molecular weight greater than100 KDa or cross-linked PAA with a linear backbone molecular weightbetween adjacent crosslinks (Mc) greater than 10 KDa.

The present self-sealing media overcome the limitations of currentlyavailable products that only seal upon exposure to aqueous-basedsolutions containing up to about 40% organic solvents. This inventionprovides products that block a spectrum of solutions from 100% aqueoussolutions to 100% polar organic solutions. The organic solvent blockingmedia in some embodiments of the present invention are useful in avariety of applications including but not limited to the following:pipette tip filter, serological pipette filter, in line filter, vent,non-mechanical check valve, safety valve, vent for a battery, vent forinkjet cartridges, vent for liquid containers and suction canister. Theorganic solvent blocking media can also be used as a gas vent and aliquid stopper for any device that needs to prime a container or asection of the device to remove air and fill with liquid. Thisfacilitates greater pumping efficiency while preventing spills fromcontaminating a pumping device. The organic solvent blocking media canallow the air and gas to escape from the device but not the liquid. Thedevices include but are not limited to liquid pumps, especially forpumping liquid containing organic solvents and acids; solution fillingand spraying devices, such as coating sprayers and ink jet printers.

In this patent application, all liquid solution mixture concentrationsare based on volume unless otherwise indicated. For example, a 40%isopropyl alcohol (IPA) aqueous solution means 40% by volume is IPA and60% by volume is water. All solid powder blends are based on weightunless they are specifically noticed, for example 20% additive and 80%thermoplastic powder means the blends have 20% by weight of additivesand 80% by weight of thermoplastic powder.

The new porous self-sealing media of the present invention can blockinorganic and organic solutions at concentrations of 40% or more. Thepresent invention also provides self-sealing media that block aqueoussolutions of inorganic acids or organic acids at concentrations of from0% to 100%. Use of these media provides a safer environment for transferof highly corrosive inorganic acids and organic acids.

In some embodiments, the porous plastic self-sealing media disclosedherein block basic aqueous solutions comprised of from about 0% to 100%,5% to 95%, 10% to 90%, 15% to 85%, or 20% to 80% bases at 2 psipressure.

Absorbent Materials

The present self-sealing media comprise an absorbent material whichrapidly expands as it absorbs water and polar organic solvents. Indifferent embodiments, absorbent materials in this invention aretypically classified as non cross-linked or lightly cross-linkedpolyacrylic acids (PAAs). In some embodiments the PAAs are notneutralized. As defined herein, lightly cross-linked means that thecross-linking density is less than about 0.5%, less than about 0.2% orless than about 0.1%. Traditional super absorbent materials aregenerally not useful in the present invention. Many super absorbentmaterials are quickly neutralized and form salts, or are highlycross-linked. Salt formation and a high degree of crosslinking decreasessolubility and dissolution speed in organic solvents and solutions, andin acidic solutions. Although traditional super absorbent materials workwell for aqueous solutions, they generally do not dissolve in polarorganic solvents or block a solution containing more than 40% organicsolvents. This is one reason why current products fail to blockorganic-based solutions or an aqueous-based solutions with more than 40%organic solvents.

In some embodiments, powdered PAA is useful in embodiments of thepresent invention as an additive for improving organic solvent blockingproperties of the porous thermoplastic media. Molecular weights of thePAA greater than about 100 KDa may be employed. PAA of at least 750 KDa,1,250 KDa, 3,000 KDa, 4,000 KDa, 10,000 KDa or 100,000 KDa may beemployed. Lower molecular weight PAA or lightly cross-linked PAA mayalso be employed. For cross-linked PAA, the linear backbone molecularweight between the adjacent crosslinks (Mc) are greater than about 10KDa, 50 KDa, 100 KDa, 500 KDa, 1,000 KDa, 2,000 KDa, 4,000 KDa, 10,000KDa, or greater than 100,000 KDa. Particulate forms of PAA may beemployed. In one embodiment, linear non cross-linked PAA powder ispreferred. Non cross-linked PAA, includes linear and branched PAA.

In other embodiments, polymers and copolymers that may function asabsorbent materials inorganic solvent blocking media are linear chainpoly(methacrylic acid), linear chain polyacrylamide and linear chainpolyhydroxyethylmethacrylate. These polymers are preferred in linearchain form, or with crosslinking less than about 0.5%, less than about0.2% or less than about 0.1%. The terms powder and particle are usedinterchangeably in this application.

In some embodiments, PAA powder is mixed with particles of thermoplasticto make a uniform dry blend. The weight ratio of PAA to thermoplastic(PAA:plastic) may be from about 1% to about 45%, from about 3% to about40%, from about 5% to about 35%, or from about 10% to about 30%, (allexpressed as wt % of the blend of absorbents and thermoplastics).

In some embodiments, the absorbent material in the sintered porousmatrix is from about 1% to about 45%, from about 3% to about 40%, fromabout 5% to about 35%, or from about 10% to about 30%, by weight of thesintered porous matrix.

PAA powders are available from Sigma Aldrich Corporation (St. Louis,Mo., US). They also are available from Lubrizol Corporation (Wickliffe,Ohio, US), under the trade name of CARBOPOL, PEMULEN, and NOVEON, BASFunder the trade name of DISPEX, and EVONIK under the trade name ofDEGAPAS. Similar products can be purchased from the following companies,Nippon Shokubai, Mitsubishi chemical, Dow Chemicals, and LG Chemicals

In some embodiments, other absorbent materials, includingcarboxymethylcellulose (CMC) and other superabsorbent materials can beblended together with PAA powder and thermoplastic powder to formsintered self-sealing porous matrix. Superabsorbents that can be addedinto PAA and thermoplastic blends include, but are not limited to:hydrolyzed starch acrylonitrile graft copolymer, acrylonitrilecopolymer, hydrolyzed acrylonitrile copolymer; neutralizedstarch-acrylic acid graft copolymer; saponified acrylic acid ester-vinylacetate copolymer; acrylamide copolymer; modified cross-linked polyvinylalcohol; neutralized cross-linked polyacrylic acid; polyacrylate salts;neutralized cross-linked isobutylene-maleic anhydride copolymers; andsalts and mixtures thereof. In one embodiment, superabsorbents aresodium polyacrylic acid and the sodium salt of poly (2propenamide-co-2-propenoic acid). Adding absorbent materials to the PAAand thermoplastic blends is for achieving optimized results for optimalwide range solution blocking performance. The amount of absorbentmaterials in the blend can vary from 0.1% to 20%, or from 1% to 10% (wt%).

PAA and other additives, such as CMC and other superabsorbent powdersshould be fine and substantially uniformly mixed with thermoplasticpowder before sintering into a substantially uniform distribution insidethe sintered porous matrix. In some embodiments, the particle size ofthe PAA and other additives is less than or equal to the particle sizeof the thermoplastic powder, for example less than about 100 microns,less than about 50 microns, or less than about 10 microns. In someembodiments, the absorbent material in the sintered porous matrix isfrom about 1% to about 45%, from about 3% to about 40%, from about 5% toabout 35%, or from about 10% to about 30%, by weight of the sinteredporous matrix.

Thermoplastics

Thermoplastics which may be employed include but are not limited to highdensity polyethylene (HDPE), low density polyethylene (LDPE), very highmolecular weight polyethylene (VHMWPE) and ultrahigh molecular weightpolyethylene (UHMWPE). Other thermoplastics which may be used includepolypropylene, ethylene vinyl acetate (EVA), polyesters, polyamides,polystyrene and polyvinylidene fluoride (PVDF).

Polyethylene, in one embodiment, comprises high density polyethylene(HDPE). High density polyethylene, as used herein, refers topolyethylene having a density ranging from about 0.92 g/cm³ to about0.97 g/cm³. In some embodiments, high density polyethylene has a degreeof crystallinity (% from density) ranging from about 50 to about 90.HDPE has a molecular weight between about 100,000 Daltons (Da) to500,000 Da.

In another embodiment, polyethylene comprises ultrahigh molecular weightpolyethylene (UHMWPE). Ultrahigh molecular weight polyethylene, as usedherein, refers to polyethylene having a molecular weight greater than1,000,000 Da, in some embodiments between 3,000,000 Da and 6,000,000 Da.

In another embodiment, polyethylene comprises very high molecular weightpolyethylene (VHMWPE). Very high molecular weight polyethylene, as usedherein, refers to polyethylene having a molecular weight greater than300,000 Da and less than 1,000,000 Da.

Elastomers

Elastomers may be optionally employed in the compositions of the presentinvention. Elastomeric particles can be rubbers, vulcanized polymers,thermoplastic elastomers, thermoplastic polyurethane, block copolymer ofbutadiene and polystyrene, copolymer of styrene-butadiene-styrene (SBS),and copolymer of styrene-ethylene-butadiene-styrene (SEBS), copolymer ofpolypropylene and polyethylene, etc. Elastomers may be employed inamounts of 0.1% to about 25%, or from about 1% to about 20%, or fromabout 5% to about 15% (expressed as wt % of the blend of absorbents andthermoplastics).

Color Change Indicators

Color change indicators may be optionally employed in the compositionsof the present invention. Color change indicators may be added to theporous organic solvent blocking media to show the extent of contact ofthe media with a liquid. In one embodiment, color change indicators areadded before sintering. In some embodiments, a color change indicatorcomprises an inorganic or organic dye, including food grade dyes, azocompounds, or azo dyes. In some embodiments, color change indicators donot comprise inorganic salts, including transition metal salts. In someembodiments, color change indicators may be in particle form and aregenerally uniformly distributed in the sintered porous self-sealingmedia

In some embodiments, a color change indicator comprises FD&C Blue No. 1,FD&C Blue No. 2, FD&C Green No. 3, FD&C Red No. 40, FD&C Red No. 3, FD&CYellow No. 5, FD&C Yellow No. 6, Solvent Red 24, Solvent Red 26, SolventRed 164, Solvent Yellow 124, Solvent Blue 35, or combinations thereof.

Color change indicators, according to some embodiments, demonstrate a pHdependency on the color produced. As a result, color change indicators,in some embodiments, indicate not only liquid contact with the barriercomposition but the relative pH of the contacting liquid as well. Colorchange indicators demonstrating a pH dependency, in some embodiments,comprise methyl violet, eosin yellow, malachite green, thymol blue,methyl yellow, bromophenol blue, Congo red, methyl orange, bromocresolgreen, methyl red, litmus, bromocresol purple, bromophenol red,bromothymol blue, phenol red, neutral red, naphtholphthalein, cresolred, phenolphthalein, thymolphthalein, alkali blue, Alizarin Yellow R,indigo carmine, epsilon blue, or combinations thereof.

Color changing agents that are soluble in organic solvents may also beused, for example fat soluble dyes, such as Sudan I, II, III, IV andclofazimine etc.

Color change indicators may be employed in amounts of about 0.001% toabout 2%, about 0.005% to about 1%, about 0.01% to about 0.5% (expressedas wt % of the blend of absorbent and thermoplastic).

Method of Making Porous Plastic Self-Sealing Media

The present self-sealing porous media comprising an absorbent materialand a thermoplastic, are made through a sintering process. A mixture ofthese materials in powder or particle form is sintered at temperaturesof about 250° F. to about 580° F. depending on the specificthermoplastic employed. These self-sealing media are generally moldedinto the desired shape. The sintering process can be conducted atambient pressure or under increased pressure. The pressure can be from 1PSI to 100 PSI. The mixtures of these materials are filled into moldcavities through gravity or vibrational processes. Porous self-sealingmedia can also be made into a sheet form which can be die cut sheet intodesired shapes.

In one embodiment, a blend of PAA powder and thermoplastic particles, orPAA powder, thermoplastic particles and CMC or other superabsorbentpowder is sintered at temperatures of about 250° F. to about 580° F.depending on the specific thermoplastic employed. Appropriate sinteringtemperatures for specific thermoplastics are known to one of ordinaryskill in the art. The duration of heating and cooling cycles depends onthe part size, mold design and desired physical properties. Thesevariables are known to one of ordinary skill in the art.

Properties of Porous Self-sealing Media

Physical Chemical Properties

In one embodiment the average pore size of the porous self-sealing mediais from about 1 micron to about 200 microns, from about 5 microns toabout 100 microns, or from about 10 microns to about 50 microns. Theaverage pore size is determined by a mercury porosimetry using the ASTMD4404 method.

The porosities the porous self-sealing media disclosed herein are fromabout 10% to about 70%, or from about 20% to about 60%, or from about30% to about 50%.

Functional Properties

The porous self-sealing media can seal and block aqueous solutions,mixtures of water and organic solvents, and organic solvents. Thepercentage of organic solvents in the aqueous solution can be from 0% to50%, 0% to 60%, 0% to 70%, 0% to 80%, 0% to 90% or 0% to 100% (vol %).The percentage of organic solvents in the aqueous solution can begreater than 40%, can be less than 80% or between about 40% to about50%, about 40% to about 60%, about 40% to about 70% or about 40% toabout 80%. The porous organic solvent blocking media of the inventioncan also seal and block non-aqueous based polar organic solvents, i.e.,100% polar organic solvent.

In some embodiments, the porous plastic self-sealing media of thepresent invention can block inorganic and organic solutions atconcentrations of about 40% or more. The present invention also providesself-sealing media that block aqueous solutions of inorganic acids ororganic acids at concentrations of from 0% to 100%.

In some embodiments, the porous plastic self-sealing media disclosedherein block basic aqueous solutions comprised of from about 0% to about100%, about 5% to about 95%, about 10% to about 90%, about 15% to about85%, or about 20% to about 80%, bases at 2 psi pressure.

The porous media disclosed herein may block aqueous surfactant solutioncomprised of surfactants at concentrations from about 0% to about 100%,0% to 95%, 0% to 90%, 0% to 85%, 0% to 80%, 0% to 70%, 0% to 50%, 0% to40%, 0% to 30%, 0% to 20%, 0% to 10%, 0% to 5%, or 0% to 2% at 2 psipressure.

The porous self-sealing media can block the passage of aerosolparticles. The porous self-sealing media also block passage of bacteriawith a filtration efficiency greater than 90%, 99%, or 99.9% based onASTM F 2101.

Configurations of the Sintered Porous Self-sealing Media

In one embodiment, the sintered porous self-sealing plastic media isconfigured in one layer. In other embodiments, the sintered porousself-sealing can be sandwiched between two layers of sintered porousplastic media that do not comprise self-sealing agents. In one specificembodiment the sintered porous self-sealing media is sandwiched betweentwo layers of sintered porous plastic of polyethylene. Color changeindicators may be placed in any one of the layers. In some embodiments,the color change indicators FD&C Blue No. 1 or FD&C Red No. 40 are usedfor good contrast to sintered white porous plastic media. In differentembodiments, elastomers may be used throughout the sintered porousself-sealing media, in a single layer, or at the perimeter of the media.

Devices Comprising Self-sealing Media

In different embodiments, the self-sealing media can be incorporatedinto numerous devices. The self-sealing media can be placed into ahousing inside a device. These include, but are not limited to,containers, pipette tips, valves, vents, liquid delivery systems, andsyringe caps. Other potential uses for, and devices comprising, theself-sealing media disclosed herein include, but are not limited to, theprotection of transducers, ink pen vents, the protection of vacuum pumpsand/or systems, the protection of pneumatic components, use in the highspeed filling of containers such as those used for batteries andbeverages, emergency spill valves for chemical containers such as drumsand bottles as well as those used on trains and other vehicles, “burp”or “blow-out” valves, use in the filling of refrigerant, brake, orhydraulic systems, and vents in items such as ink-jet cartridges anddisk drives.

Since the self-sealing media are porous, they can act as a safety valve,for example located in or on a container above the level of the organicfluid. Since these media are porous, they permit the passage of gas,thereby functioning as a vent. If the container were to tip, the porousself-sealing media would seal upon contact with the organic fluid,thereby preventing or retarding the organic solvent from spilling out ofthe container.

One embodiment of porous self-sealing media is its use as a pipette tipfilter to prevent handheld pipettors or automatic liquid pipettingmachines from contamination by accidental over pipetting of solutionscontaining more than 40% organic solvents or solutions of acids orbases.

Another embodiment of porous self-sealing media is its use as vent forsuction devices to prevent contamination of suction devices or vacuumsystems by accidental over suction of solutions containing more thanabout 40% organic solvents. The suction devices include but are notlimited to a suction canister in a medical or scientific device or avacuum cleaner for cleaning organic solvent spills. The self-sealingmedia for use in a suction device such as a suction canister may be anyshape to fit within the gas flow path in the devise. The media mayappear as shown in FIG. 2. In another embodiment, the media may be inthe form of a disc for insertion at another location in the canister,for example near the filter lid.

Yet another embodiment of porous self-sealing media is its use as a ventfor an ink cartridge to allow air to pass to balance the negativepressure inside the cartridge during use, and at the same time, toprevent ink with high organic solvent content from leaking when thecartridge is tipped over.

Still another embodiment of porous self-sealing media is its use as avent for organic solvent filling devices to allow air to pass to balancethe negative pressure inside the device during the filling process, andat same time, to prevent organic solvent from leaking when the device istipped over.

Since the self-sealing organic solvent blocking media are also blockinorganic and organic acidic solutions, they can act as a safety valvefor containers of inorganic or organic acids. These media can preventthe spill of solutions of inorganic or organic acids from the containerswhen the containers are tipped.

In one embodiment, the self-sealing media are used as a vent for an acidbased battery, such as a car battery, a golf car battery and a truckbattery. An example of a vent for a battery is shown as a frit labeledas item 42 in FIG. 4 of U.S. pat. No. 6,110,617. In this embodiment, theself-sealing media allows gas to pass in a normal position to preventdangerous hydrogen gas from building up inside the battery. At the sametime the self-sealing media also block the leaking of hazardous acidswhen the automobile is involved in an accident or the battery is tippedover during transport. Current acid battery vents do not block theleakage of acid.

In one embodiment the self-sealing media are used as a pipette tipfilter to prevent handheld pipettors or automatic liquid pipettingmachines from contamination by accidental over pipetting of solutionscontaining inorganic or organic acids.

Organic Solutions

Organic solutions which may be blocked with the porous media disclosedherein are polar organic solvents that are miscible with water. Theyinclude but are not limited to the following: alcohols, such asmethanol, ethanol, propanol, isopropanol, butanol etc.; ketones, such asacetone or methylethylketone (MEK); aldehydes, such as formaldehyde oracetaldehyde; organic acids, such as acetic acid, formic acid, or lacticacid; amines, such as ammonia, methylamine, dimethylamine,trimethylamine, ethylamine, diethylamine, triethylamine, ethanolamine,anilines, or pyridines; dimethylsulfoxide (DMSO), dimethylformamide(DMF), dimethylacetamide (DMAC), N-Methyl-2-pyrrolidone (NMP),epichlorohydrin, tetrahydrofuran (THF), and acetonitrile. Organicsolutions also include but are not limited to methanol, acetone,acrylonitrile, pyridine, acetic acid, trifluoroacetic acid (TFA),butanol, ethanol, dioxane, dimethoxyethane, diethanolamine,formaldehyde, and ethylene glycol.

Organic solutions may also contain other organic compounds that havelimited miscibility with water, but are miscible with organic solvents,such as phenols, cyclohexanone, and aromatic acids.

Acidic Liquid Solutions

Acidic aqueous solutions that may be blocked by the porous mediadisclosed herein include solutions of organic acids and solutions ofinorganic acids. Organic acids include, but are not limited to, aceticacid, trifluoroacetic acid, trichloroacetic acid, formic acid, lacticacid, citric acid, oxalic acid, tartaric acid, gluconic acid,methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid,p-toluenesulfonic acid, and trifluomethanesulfonic acid. Inorganic acidsinclude, but are not limited to, sulfuric acid, fluorosulfuric acid,nitric acid, phosphoric acid, fluoroboric acid, fluoroantimonic acid,chromic acid, boric acid, hydrochloric acid, hydrobromic acid,hydroiodic acid, hypochlorous acid, chlorous acid, chloric acid andperchloric acid.

Porous media disclosed herein may block acidic aqueous solutionscomprised of from about 0% to about 100%, 0% to 95%, 0% to 90%, 0% to85%, or 0% to 80%, 0% to 60%, 0% to 50%, or 0% to 40% acid at 2 psipressure.

Basic Liquid Solutions

Basic aqueous solutions may be blocked by the porous media disclosedherein include solutions of organic bases and solutions of inorganicbases. Organic bases include, but are not limited to, methylamine,ethylamine, ethylenediamine, ammonia, and other water soluble organicamines. Inorganic bases include sodium hydroxide, potassium hydroxide,cesium hydroxide, and lithium hydroxide. Porous media disclosed hereinmay block basic aqueous solutions comprised of from about 0% to 100%, 5%to 95%, 10% to 90%, 15% to 85%, or 20% to 80%, bases at 2 psi pressure.

Surfactant Liquid Solutions

Aqueous solutions containing surfactants may be blocked by the porousmedia disclosed herein. Such surfactants include, but are not limitedto, anionic surfactants, such as sodium dodecylsulfate (SDS); cationicsurfactants, such as cetyltrimethylammonium bromide (CTAB), non-ionicsurfactants such as nonyl phenoxypolyethoxylethanol (NP-40), Tween-20,Triton-100, and amphoteric surfactants, such as3-[(3-Cholamidopropyl)dimethylammonio]-1-propanesulfonate.Fluorosurfactants may also be blocked, such as Zonyl® fluorosurfactantfrom DuPont. Many other surfactants as known to one of ordinary skill inthe art may also be blocked by these porous media. The porous mediadisclosed herein may block aqueous surfactant solution comprised ofsurfactants at concentrations from about 0% to 100%, 0% to 95%, 0% to90%, 0% to 85%, 0% to 80%, 0% to 70%, 0% to 50%, 0% to 40%, 0% to 30%,0% to 20%, 0% to 10%, 0% to 5%, or 0% to 2% at 2 psi pressure.

In one embodiment, the porous self-sealing medium comprises a sinteredmixture of thermoplastic particles and PAA powders.

In one embodiment, the porous self-sealing medium comprises a sinteredmixture of thermoplastic particles and PAA powders, wherein the PAApowder is linear PAA with a molecular weight greater than 100 KDa orcross-linked PAA with a linear backbone molecular weight betweenadjacent crosslinks (Mc) greater than 10 KDa.

In another embodiment, the porous self-sealing medium comprises asintered mixture of thermoplastic particles, PAA powders and CMCparticles.

In yet another embodiment, the porous self-sealing medium comprises asintered mixture of thermoplastic particles, PAA powders and superabsorbent particles.

In one embodiment, the porous self-sealing medium comprises a sinteredmixture of thermoplastic particles, elastomeric particles and PAApowders.

In another embodiment, the porous self-sealing medium comprises asintered mixture of thermoplastic particles, elastomeric particles, PAApowders and CMC particles.

In yet another embodiment, the porous self-sealing medium comprises asintered mixture of thermoplastic particles, elastomeric particles, PAApowders and superabsorbent particles.

In another embodiment, the porous self-sealing medium comprises asintered mixture of thermoplastic particles, PAA powders and colorchange indicators.

In yet another embodiment, the porous self-sealing medium comprises asintered mixture of thermoplastic particles, elastomeric particles, PAApowders and color change indicators.

The performance of the porous plastic self-sealing media described inthe examples as products A through P were tested as described in thisparagraph. This embodiment of the porous plastic self-sealing media wasas a pipette tip filter. All testing described in the following exampleswas performed in a 200 μl pipette tip. The porous plastic self-sealingfilters were inserted at the location in the pipette tip correspondingto a location about 50 μl from the tip opening which contacts liquid.The pipette device was set at 200 μl to pull liquid through the porousfilter and cause an over-pipetting event. The filtered pipette tips weresecurely mounted on the barrel of the pipette device, and the pipetteplunger was pushed down and quickly released (thumb quickly removed fromthe plunger). The liquid level was observed. If the liquid passed thefilter, the filter was labeled as a failure. If the liquid did not reachthe top of the filter, the filter was labeled as successfully blockingthe fluid. Various solutions were tested as shown in Tables 1 through 4.The differential pressure applied to the filters during the pipettingprocess is about 2 psi or 0.138 bar.

The average pore size and pore volume of the sintered porous media inthis invention is measured by a mercury intrusion porosimeter followingthe ASTM D 4404 method.

The following examples will serve to further illustrate the presentinvention without, at the same time, however, constituting anylimitation thereof. On the contrary, it is to be clearly understood thatresort may be had to various embodiments, modifications and equivalentsthereof which, after reading the description herein, may suggestthemselves to those skilled in the art without departing from the spiritof the invention.

EXAMPLE 1

Product A: A powder blend comprising 90% (weight) of GUR very highmolecular weight polyethylene (VHMWPE) with median particle size of 130microns (Ticona, Florence, Ky., US) and 10% polyacrylic acid powder withmolecular weight of 750,000 Da (Sigma Aldrich, St. Louis, Mo., US) wassintered in an aluminum mold at 350° F. for 3 minutes and cooled to roomtemperature in 5 minutes. The resulting filters had an average pore sizeof 25 microns and average pore volume of 40%.

EXAMPLE 2

Product B: A powder blend comprising 90% (weight) of GUR ultrahighmolecular weight polyethylene (UHMWPE) with median particle size of 60microns (Ticona, Florence, Ky., US) and 10% polyacrylic acid powder withmolecular weight of 750,000 Da (Sigma Aldrich, St. Louis, Mo., US) wassintered in an aluminum mold at 360° F. for 3 minutes and cooled to roomtemperature in 5 minutes. The resulting filters had an average pore sizeof 15 microns and average pore volume of 40%.

EXAMPLE 3

Product C: A powder blend comprising 90% (weight) of ultrahigh molecularweight polyethylene (UHMWPE) with median particle size of 30 microns(Mitsui, Tokyo, Japan) and 10% polyacrylic acid powder with molecularweight of 750,000 Da (Sigma Aldrich, St. Louis, Mo., US) was sintered inan aluminum mold at 360° F. for 3 minutes and cooled to room temperaturein 5 minutes. The resulting filters had an average pore size of 10microns and average pore volume of 40%.

EXAMPLE 4

Product D: A powder blend comprising 80% (weight) of GUR very highmolecular weight polyethylene (VHMWPE) with median particle size of 130microns (Ticona, Florence, Ky., US), 10% polyacrylic acid powder withmolecular weight of 750,000 Da (Sigma Aldrich, St. Louis, Mo., US) and10% high molecular weight carboxymethylcellulose (CMC) (Tic Gums, WhiteMarsh, Md., US) was sintered in an aluminum mold at 350° F. for 3minutes and cooled to room temperature in 5 minutes. The resultingfilters had an average pore size of 27 microns and average pore volumeof 40%.

EXAMPLE 5

Product E: A powder blend comprising 90% (weight) of GUR very highmolecular weight polyethylene (VHMWPE) with median particle size of 130microns (Ticona, Florence, Ky., US) and 10% Carbopol 907 powder(Lubrizol, Wickliffe, Ohio, US) was sintered in an aluminum mold at 350°F. for 3 minutes and cooled to room temperature in 5 minutes. Theresulting filters had an average pore size of 25 microns and averagepore volume of 40%.

EXAMPLE 6

Product F: A powder blend comprising 90% (weight) of GUR ultrahighmolecular weight polyethylene (UHMWPE) with median particle size of 60microns (Ticona, Florence, Ky., US) and 10% Carbopol 907 powder(Lubrizol, Wickliffe, Ohio, US) was sintered in an aluminum mold at 360°F. for 3 minutes and cooled to room temperature in 5 minutes. Theresulting filters had an average pore size of 15 microns and averagepore volume of 40%.

EXAMPLE 7

Product G: A powder blend comprising 90% (weight) of ultrahigh molecularweight polyethylene (UHMWPE) with media particle size of 30 microns(Mistui, Tokyo, Japan) and Carbopol 907 powder (Lubrizol, Wickliffe,Ohio, US) was sintered in an aluminum mold at 360° F. for 3 minutes andcooled to room temperature in 5 minutes. The resulting filters had anaverage pore size of 10 microns and average pore volume of 40%.

EXAMPLE 8

Product H: A powder blend comprising 80% (weight) of GUR very highmolecular weight polyethylene (VHMWPE) with media particle size of 130microns (Ticona, Florence, Ky., US), 10% Carbopol 907 powder (Lubrizol,Wickliffe, Ohio, US) and 10% high molecular weightcarboxymethylcellulose (CMC) (Tic Gums, White Marsh, Md., US) wassintered in an aluminum mold at 350° F. for 3 minutes and cooled to roomtemperature in 5 minutes. The resulting filters had an average pore sizeof 27 microns and average pore volume of 40%.

EXAMPLE 9

Product I: A powder blend comprising 100% (weight) of GUR very highmolecular weight polyethylene (VHMWPE) with media particle size of 130microns (Ticona, Florence, Ky., US) was sintered in an aluminum mold at350° F. for 3 minutes and cooled to room temperature in 5 minutes. Theresulting filters had an average pore size of 25 microns and averagepore volume of 40%.

EXAMPLE 10

Product J: A powder blend comprising 100% (weight) of GUR ultrahighmolecular weight polyethylene (UHMWPE) with media particle size of 60microns (Ticona, Florence, Ky., US) was sintered in an aluminum mold at360° F. for 3 minutes and cooled to room temperature in 5 minutes. Theresulting filters had an average pore size of 15 microns and averagepore volume of 40%.

EXAMPLE 11

Product K: A powder blend comprising 90% (weight) of GUR very highmolecular weight polyethylene (VHMWPE) with media particle size of 130microns (Ticona, Florence, Ky., US) and 10% high molecular weightcarboxymethylcellulose (CMC) (Tic Gums, White Marsh, Md., US) wassintered in a aluminum mold at 350° F. for 3 minutes and cooled to roomtemperature in 5 minutes. The resulting filters had an average pore sizeof 25 microns and average pore volume of 40%.

EXAMPLE 12

Product L: A powder blend comprising 90% (weight) of GUR ultrahighmolecular weight polyethylene (UHMWPE) with media particle size of 60microns (Ticona, Florence, Ky., US) and 10% high molecular weightcarboxymethylcellulose (CMC) (Tic Gums, White Marsh, Md., US) wassintered in a aluminum mold at 360° F. for 3 minutes and cooled to roomtemperature in 5 minutes. The resulting filters had an average pore sizeof 15 microns and average pore volume of 40%.

TABLE 1 Blocking properties for isopropanol (IPA) and water mixturesolutions for products A through L. Prod- DI 20% 40% 60% 80% 100% uctwater IPA IPA IPA IPA IPA A Block Block Block Block Block Fail B BlockBlock Block Block Block Block C Block Block Block Block Block Block DBlock Block Block Block Block Fail E Block Block Block Block Block FailF Block Block Block Block Block Block G Block Block Block Block BlockBlock H Block Block Block Block Block Fail I Fail Fail Fail Fail FailFail J Block Fail Fail Fail Fail Fail K Block Block Block Fail Fail FailL Block Block Block Fail Fail Fail

The results in Table 1 show that the combination of PAA with UHMWPE orVHMWPE was superior to UHMWPE or VHMWPE alone, or UHMWPE or VHMWPEcombined with CMC in blocking passage of isopropanol, particularly athigher concentrations of IPA.

TABLE 2 Blocking properties for DMSO and water mixture solutions: Prod-DI 20% 40% 60% 80% 100% uct water DMSO DMSO DMSO DMSO DMSO A Block BlockBlock Block Block Fail B Block Block Block Block Block Block C BlockBlock Block Block Block Block D Block Block Block Block Block Fail EBlock Block Block Block Block Fail F Block Block Block Block Block BlockG Block Block Block Block Block Block H Block Block Block Block BlockFail I Fail Fail Fail Fail Fail Fail J Block Fail Fail Fail Fail Fail KBlock Block Block Fail Fail Fail L Block Block Block Fail Fail Fail

The results in Table 2 show that the combination of PAA with UHMWPE orVHMWPE was superior to UHMWPE or VHMWPE alone, or UHMWPE or VHMWPEcombined with CMC in blocking passage of DMSO, particularly at higherconcentrations of DMSO.

TABLE 3 Blocking properties for methanol and water mixture solutions:Prod- DI 20% 40% 60% 80% 100% uct water methanol Methanol Methanolmethanol Methanol A Block Block Block Block Block Block B Block BlockBlock Block Block Block C Block Block Block Block Block Block D BlockBlock Block Block Block Block E Block Block Block Block Block Block FBlock Block Block Block Block Block G Block Block Block Block BlockBlock H Block Block Block Block Block Block I Fail Fail Fail Fail FailFail J Block Fail Fail Fail Fail Fail K Block Block Block Fail Fail FailL Block Block Block Fail Fail Fail

The results in Table 3 show that the combination of PAA with UHMWPE orwith VHMWPE was superior to either UHMWPE or VHMWPE alone, or to UHMWPEor VHMWPE combined with CMC, in blocking the passage of methanol,particularly at higher concentrations of methanol, including 100%methanol.

EXAMPLE 13

Product M: A powder blend comprising 90% (weight) of GUR Ultrahighmolecular weight polyethylene (UHMWPE) with median particle size of 60microns (Ticona, Florence, Ky., US) and 10% Carbopol® 941 powder(Lubrizol, Wickliffe, Ohio, US) was sintered in an aluminum mold at 350°F. for 3 minutes and cooled to room temperature in 5 minutes. Theresulting filters had an average pore size of 15 microns and averagepore volume of 38%.

EXAMPLE 14

Product N: A powder blend comprising 90% (weight) of GUR very highmolecular weight polyethylene (VHMWPE) with median particle size of 130microns (Ticona, Florence, Ky., US) and 10% Carbopol 941 powder(Lubrizol, Wickliffe, Ohio, US) was sintered in an aluminum mold at 350°F. for 3 minutes and cooled to room temperature in 5 minutes. Theresulting filters had an average pore size of 25 microns and averagepore volume of 40%.

EXAMPLE 15

Product O: A powder blend comprising 90% (weight) of GUR very highmolecular weight polyethylene (VHMWPE) with media particle size of 130microns (Ticona, Florence, Ky., US) and 10% high molecular weightcarboxymethyl cellulose (CMC) (Tic Gums, White Marsh, Md., US) wassintered in an aluminum mold at 350° F. for 3 minutes and cooled to roomtemperature in 5 minutes. The resulting filters had an average pore sizeof 27 microns and average pore volume of 40%.

EXAMPLE 16

Product P: A powder blend comprising 100% (weight) of ultrahighmolecular weight polyethylene (UHMWPE) with media particle size of 30microns (Mistui, Tokyo, Japan) was sintered in an aluminum mold at 360°F. for 3 minutes and cooled to room temperature in 5 minutes. Theresulting filters had an average pore size of 10 microns and averagepore volume of 38%.

EXAMPLE 17

The comparative performances for different barrier media products M, N,0, and P from Examples 13 through 16 are shown in Table 4.

Table 4: This table shows results for the blocking properties fordeionized (DI) water, isopropanol (IPA), DMSO, methanol, acetone, DMAC,NMP, DMF, acrylonitrile, THF, pyridine, acetic acid, HCl, TFA, butanol,ethanol, dioxane, dimethoxyethane, diethanolamine, formaldehyde,ethylene glycol, sodium hydroxide (NaOH), Tween 20, and SDS.

The results indicate that products M and N (each containing PAA asabsorbent), were superior in their blocking properties when compared toproducts O (CMC as the only absorbent) and P (no absorbent). This wasespecially evident at higher concentrations of many of the testedsolvents.

The new porous plastic self-sealing media showed superior performancecompared to currently available commercial products in blocking aqueoussolutions of organic solvents. Current self-sealing media could onlyblock aqueous solutions of organic solvents up to an organic solventconcentration of 40%. The organic solvents tested were: methanol,ethanol, isopropanol, butanol, acetone, pyridine, dimethylsulfoxide(DMSO), dimethylformamide (DMF), dimethylacetamide (DMAC),N-Methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), dioxane,Dimethoxyethane and acetonitrile. The new media could block aqueoussolutions of these organic solvents at the concentrations of at least of60%.

The new porous plastic self-sealing media showed superior performancecompared to currently available commercial products in blocking liquidacidic solutions. Currently available self-sealing media could not blockacidic aqueous solution with acid concentrations over 5%. The new porousplastic self-sealing media blocked acidic solutions comprised of atleast 40% acid. The tested acids were acetic acid, HCl, andtrifluoroacetic acid.

Prod- DI 20% 40% 60% 80% 100% uct water IPA IPA IPA IPA IPA M BlockBlock Block Block Block Fail N Block Block Block Block Block Fail OBlock Block Block Fail Fail Fail P Block Fail Fail Fail Fail Fail Prod-DI 20% 40% 60% 80% 100% uct water DMSO DMSO DMSO DMSO DMSO M Block BlockBlock Block Block Fail N Block Block Block Block Block Fail O BlockBlock Block Fail Fail Fail P Block Block Fail Fail Fail Fail Prod- DI20% 40% 60% 80% 100% uct water Methanol Methanol Methanol MethanolMethanol M Block Block Block Block Block Block N Block Block Block BlockBlock Block O Block Block Block Fail Fail Fail P Block Fail Fail FailFail Fail Prod- DI 20% 40% 60% 80% 100% uct water Acetone AcetoneAcetone Acetone Acetone M Block Block Block Block Block Fail N BlockBlock Block Block Block Fail O Block Block Block Fail Fail Fail P BlockFail Fail Fail Fail Fail Prod- DI 20% 40% 60% 80% 100% uct water DMACDMAC DMAC DMAC DMAC M Block Block Block Block Block Fail N Block BlockBlock Block Fail Fail O Block Block Block Fail Fail Fail P Block FailFail Fail Fail Fail Prod- DI 20% 40% 60% 80% 100% uct water NMP NMP NMPNMP NMP M Block Block Block Block Block Fail N Block Block Block BlockFail Fail O Block Block Block Fail Fail Fail P Block Fail Fail Fail FailFail Prod- DI 20% 40% 60% 80% 100% uct water DMF DMF DMF DMF DMF M BlockBlock Block Block Block Fail N Block Block Block Block Fail Fail O BlockBlock Block Fail Fail Fail P Block Fail Fail Fail Fail Fail 20% 40% 60%80% 100% Prod- DI Acrylo- Acrylo- Acrylo- Acrylo- Acrylo- uct waternitrile nitrile nitrile nitrile nitrile M Block Block Block Block BlockFail N Block Block Block Block Fail Fail O Block Block Block Fail FailFail P Block Fail Fail Fail Fail Fail Prod- DI 20% 40% 60% 80% 100% uctwater THF THF THF THF THF M Block Block Block Block Block Fail N BlockBlock Block Block Block Fail O Block Block Block Fail Fail Fail P BlockFail Fail Fail Fail Fail Prod- DI 20% 40% 60% 80% 100% uct waterPyridine Pyridine Pyridine Pyridine Pyridine M Block Block Block BlockBlock Fail N Block Block Block Block Fail Fail O Block Block Block FailFail Fail P Block Fail Fail Fail Fail Fail 20% 40% 60% 80% 100% Prod- DIAcetic Acetic Acetic Acetic Acetic uct water Acid Acid Acid Acid Acid MBlock Block Block Block Block Fail N Block Block Block Block Fail Fail OBlock Fail Fail Fail Fail Fail P Block Fail Fail Fail Fail Fail Prod- DI5% 10% 20% 30% 37% uct water HCl HCl HCl HCl HCl M Block Block BlockBlock Block Block N Block Block Block Block Block Block O Block FailFail Fail Fail Fail P Block Block Block Block Block Block Prod- DI 20%40% 60% 80% 100% uct water TFA TFA TFA TFA TFA M Block Block Block FailFail Fail N Block Block Block Fail Fail Fail O Block Fail Fail Fail FailFail P Block Fail Fail Fail Fail Fail Prod- DI 20% 40% 60% 80% 100% uctwater Butanol Butanol Butanol Butanol Butanol M Block Block Block BlockBlock Fail N Block Block Block Block Block Fail O Block Block Fail FailFail Fail P Block Fail Fail Fail Fail Fail Prod- DI 20% 40% 60% 80% 100%uct water Ethanol Ethanol Ethanol Ethanol Ethanol M Block Block BlockBlock Block Fail N Block Block Block Block Block Fail O Block BlockBlock Fail Fail Fail P Block Fail Fail Fail Fail Fail Prod- DI 20% 40%60% 80% 100% uct water Dioxane Dioxane Dioxane Dioxane Dioxane M BlockBlock Block Block Block Fail N Block Block Block Block Fail Fail O BlockBlock Block Fail Fail Fail P Block Fail Fail Fail Fail Fail 20% 40% 60%80% 100% Dime- Dime- Dime- Dime- Dime- Prod- DI thoxy- thoxy- thoxy-thoxy- thoxy- uct water ethane ethane ethane ethane ethane M Block BlockBlock Block Block Fail N Block Block Block Block Block Fail O BlockBlock Block Fail Fail Fail P Block Fail Fail Fail Fail Fail 20% 40% 60%80% 100% Prod- DI Diethanol- Diethanol- Diethanol- Diethanol- Diethanol-uct water amine amine amine amine amine M Block Block Block Block BlockBlock N Block Block Block Block Block Block O Block Block Block BlockBlock Block P Block Block Block Block Block Block 5% 10% 20% 30% 37%Prod- DI Formal- Formal- Formal- Formal- Formal- uct water dehyde dehydedehyde dehyde dehyde M Block Block Block Block Block Block N Block BlockBlock Block Block Block O Block Block Block Block Block Block P BlockBlock Block Fail Fail Fail Prod- DI 20% 40% 60% 80% 100% uct waterGlycerol Glycerol Glycerol Glycerol Glycerol M Block Block Block BlockBlock Block N Block Block Block Block Block Block O Block Block BlockBlock Block Block P Block Block Block Block Block Block 20% 40% 60% 80%100% Prod- DI Ethylene Ethylene Ethylene Ethylene Ethylene uct waterGlycol Glycol Glycol Glycol Glycol M Block Block Block Block Block BlockN Block Block Block Block Block Block O Block Block Block Block FailFail P Block Block Block Fail Fail Fail Prod- DI 5% 10% 20% 30% 50% uctwater NaOH NaOH NaOH NaOH NaOH M Block Block Block Block Block Block NBlock Block Block Block Block Block O Block Block Block Block BlockBlock P Block Block Block Block Block Block Prod- DI 0.01% 0.1% 0.5% 1%2% uct water Tween 20 Tween 20 Tween 20 Tween 20 Tween 20 M Block BlockBlock Block Block Block N Block Block Block Block Block Block O BlockBlock Block Block Block Block P Block Block Block Fail Fail Fail Prod-DI 0.01% 0.1% 0.5% 1% 2% uct water SDS SDS SDS SDS SDS M Block BlockBlock Block Block Block N Block Block Block Block Block Block O BlockBlock Block Block Block Block P Block Block Block Fail Fail Fail

All patents, publications and abstracts cited above are incorporatedherein by reference in their entirety. Various embodiments of theinvention have been described in fulfillment of the various objectivesof the invention. It should be recognized that these embodiments aremerely illustrative of the principles of the present invention. Numerousmodifications and adaptations thereof will be readily apparent to thoseskilled in the art without departing from the spirit and scope of thepresent invention as defined in the following claims.

What is claimed is:
 1. A porous self-sealing composition comprising asintered porous matrix of particles of an absorbent material andparticles of a thermoplastic, wherein the absorbent material comprisespolyacrylic acid, and the polyacrylic acid is linear polyacrylic acidwith a molecular weight greater than 100 KDa or cross-linked polyacrylicacid with a linear backbone molecular weight between adjacent crosslinks(Mc) greater than 10 KDa.
 2. The composition of claim 1, wherein theabsorbent material in the sintered porous matrix is from about 1% toabout 45%, from about 3% to about 40%, from about 5% to about 35%, orfrom about 10% to about 30%, by weight of the sintered porous matrix. 3.The composition of claim 1, wherein the sintered porous matrix has aporosity of from about 10% to about 70%, from about 20% to about 60%, orfrom about 30% to about 50%.
 4. The composition of claim 1, wherein thesintered porous matrix has an average pore size of from about 1 micronto about 200 microns, from about 5 microns to about 100 microns, or fromabout 10 microns to about 50 microns.
 5. The composition of claim 1,wherein the cross-linked polyacrylic acid has a cross-linking density ofless than about 0.5%, less than about 0.2% or less than about 0.1%. 6.The composition of claim 1, wherein the thermoplastic particles areselected from the group consisting of polyethylene, polypropylene andpolyvinylidene fluoride (PVDF).
 7. The composition of claim 6, whereinthe polyethylene is high density polyethylene (HDPE), low densitypolyethylene (LDPE), very high molecular weight polyethylene (VHMWPE),or ultrahigh molecular weight polyethylene (UHMWPE).
 8. The compositionof claim 1, further comprising a thermoplastic elastomer or a colorchange indicator.
 9. The composition of claim 1, further comprising anabsorbent material, CMC or a superabsorbent material.
 10. A devicecomprising the composition of claim
 1. 11. The device of claim 10,wherein the device is a pipette tip, an in line filter, a vent, a valve,a container, a non-mechanical check valve, a safety valve, a syringecap, or a suction canister.
 12. A method of making the composition claim1 comprising: providing particles of polyacrylic acid, wherein thepolyacrylic acid is linear polyacrylic with a molecular weight greaterthan 100 KDa or cross-linked polyacrylic with a the linear backbonemolecular weight between adjacent crosslinks (Mc) greater than 10 KDa;providing particles of a thermoplastic; blending the particles ofpolyacrylic acid and the particles of thermoplastic to make a mixture;adding the mixture to a mold; sintering the mixture; removing themixture from the mold.
 13. A method of blocking the passage of asolution comprising: contacting the composition of claim 1 with thesolution; and, permitting the composition to absorb the solution andseal, whereby passage of the solution is blocked by the composition. 14.The method of claim 13, wherein the solution comprises an organicsolvent or an aqueous solution of more than 40% of an organic solvent.15. The method of claim 13, wherein the solution comprises more than 5%of an inorganic acid or more than 5% of an organic acid.
 16. The methodof claim 13, wherein the contacting step occurs at about 2 psi.
 17. Themethod of claim 13, wherein the solution further comprises a surfactant.